Ok from looking at your pic you look like a decent guy im 22 my self in a relationship now but when I was single did I have a blast but thats a story for another website.
Be yourself.
Hygiene I CANT STRESS THIS ONE ENOUGH. ie brush teeth(nothing worse than bad breath kisses)showers shave deoderant etc.
Dress casual no shorts unless where called for ie beach etc. also wear a nice shirt a button up nice vneck. Avoid hats like the plague. Do your hair.
Make her laugh.
peacocking lol wear a nice watch or necklace etc to grab the girls attention after all we all know girls love shiny,trust me sounds dumb but works.
O and if all else fails drink til you can talk lol jk hope this helps man keep your head up.